Since there is nothing wrong with your current engine, you will be throwing away $2k on one of those ebay engines. $2k will buy you a used block, and new head w/all new internals from enginebuilder, and have enough left over to redo the exhaust.

Enginebuilder
New Street RV Head The rest of what you need

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed